[aaronblohowiak]

i have a question about conservation of momentum. what about losses due to friction and/or heat?

I could imagine through some interesting device a way to have thrust in one direction with the "conservation" occurring as heat radiating in all of the other directions -- is this not compatible with conservation of momentum or am i a crackpot who doesnt understand the basics (the more likely case, i am sure)

[PeterisP]

How would that heat radiate?

Electromagnetic radiation has momentum - it's small, but not zero. If you're emitting a bunch of photons (e.g. infrared photons from blackbody radiation of a hot object) more to one side than the other, then the remainder of that device will have some thrust. But that does not violate conservation of momentum, as the momentum gained by the device will equal the momentum of these photons; and the total momentum of the whole system (the device plus all the photons radiated) will be constant.

[aaronblohowiak]

Thank you!

[dodobirdlord]

Crackpot who doesn't understand the basics (not to be rude). Unlike energy, momentum is a vector quantity. A system can't disperse momentum "in all directions" because the net effect will cancel out. A bomb that has net momentum 0 still has net momentum 0 after it's been exploded.

[aaronblohowiak]

Thank you!